This study determined actual and perceived risk of Diabetes Mellitus (DM) among undergraduates in Osogbo in Southwestern Nigeria. It was a descriptive cross sectional explorative study conducted among 250 newly admitted undergraduates of Osun state University selected using multi-staged sampling method. Data on perceived and actual risk to DM were collected using pre tested self- administered semi-structured questionnaire. Data was analyzed using the SPSS software. Mean age of respondents was 21.0 2.4 years. Of the 250 students 230(92.0%) have heard about DM, 37(14.8%) were overweight and 9(3.6%) were obese. Only 11(4.4%) felt they were at risk of DM, 237(94.8%) said they were not at risk, 225(90.0%) said they can never have DM. Based on the six selected risk factors, only 64(25.6%) were at no risk, 137(54.8%) had single while 49(19.6%) were at multiple risk of DM. Of the 237 who claimed or perceived they were not at risk, only 64 (27.0%) were actually at no risk. A statistically significant relationship was found between actual DM risk and having heard about DM (p<0.05). Having heard about DM was the major predictor of congruent actual and perceived risk among studied respondents. It was concluded that incongruence between perceived and actual risk to DM exists among University undergraduates studied, an indication to step up awareness programmes about DM